QA/QC pH

QA/QC protocols:
The pH sensors are routinely monitored and calibrated using NIST Certified pH 7.0 and pH 10.0 buffer solutions. Sensors will be recovered on a monthly basis for evaluation and recalibration if needed.

QA/QC notes:
Early deployments of these sensors were subject to almost continual drift due to a fouling of the internal gel solution. Improvements in calibration protocols (including retrieving the sensors from the field and recalibrating under laboratory conditions) has improved the performance of the sensors, however, these sensors may still drift and this remains the primary cause of lower data quality. When possible, the periods of drift are corrected for by assuming a simple linear drift. These corrections should be considered approximate. The quality level assigned to the data will be due in part to whether the sensor drifted and the extent of the drift. Only when the calibration is verified to have remained stable are the data flagged as good.